Manufacture of slub effect fabrics



May 12, 1970 J.- MAJOR ET AL 3,511,064

MANUFACTURE OF SLUB EFFECT FABRICS Filed Jan. 51, 1968 lnoenlor: Jo H w M m/ 0 8 35mm Use/we 3/0:

United States Patent Int. c1. D04b 15/48 U.S. Cl. 66-125 Claims ABSTRACT OF THE DISCLOSURE A slub effect fabric is obtained by knitting in an extra yarn during the manufacture of warp knit fabric and arranging that this yarn be broken and repeatedly reintroduced to the needles according to a random pattern arrangement.

The present invention is concerned with improvements in the manufacture of slub effect fabrics and in particular to a novel slub effect fabric and method and apparatus for the production thereof.

Fabrics having a slub effect are normally produced from a specially prepared slub yarn. The preparation of this yarn involves a number of folding/ twisting operations and is hence more expensive than standardyarns. It is usually prepared from staple fibre yarns in preference to continuous filament yarns.

We have now found that a slub effect fabric can be simply and economically produced on a weft knitting machine, especially, a circular knitting machine, from a basically 100% standard continuous filament yarn. The effect is obtained by feeding an extra yarn, preferably a staple yarn, to the needles of a knitting machine whilst these are knitting the basic fabric, and arranging that the extra yarn break at frequent intervals to produce a slub effect in the fabric. The extra yarn can be introduced at any predetermined number of feed points, preferably where both cylinder and dial needles are knitting, without affecting the rate at which the. basic fabric is knitted.

The slub effect can be varied by varying the number of points at which it is fed into the basic fabric, by varying the yarn denier and by varying the manner in which it is fed into the fabric. i

Since the extra yarn giving the slub effect is knitted and not merely laid into the fabric it is firmly anchored and there is no tendency for it to be pulled out by plucking or snagging.

Accordingly therefore, from one aspect, the present invention provides a weft knitted slub effect fabric comprising a base fabric formed from one yarn and containing an extra yarn which is knitted in with the aforementioned yarn at intervals along fabric courses, said extra yarn being discontinuous in the knitted fabric.

The expression-being discontinuous in the knitted fabricmeans that there, is an absence of floats joining each portion of extra yarn knitted into the fabric.

Preferably the fabric is formed from a bulked continu ous filament yarn and preferably also the extra yarn is a staple yarn of the same type.

From another aspect the present invention provides a process for the manufacture. of a fabric having a slub effect wherein a yarn is knitted into a base fabric comprising a plurality of knitted courses, an extra yarn introduced to the knitting elements during the knitting of one course of the fabric and knitted in with the aforementioned yarn for a plurality of stitches, the said extra yarn broken 3,511,064 Patented May 12, 1970 and subsequently reintroduced to the elements to be knitted into the fabric again further along the course or in a subsequent course, the introduction of the extra yarn to the elements and the breaking thereof being repeated at intervals during the knitting of the fabric.

Conveniently the extra yarn may be introduced to the knitting needles via a positive feed attachment to the knitting machine, which attachment incorporates a tube through which are blown to forward the yarn to the knitting needles and which has a cutting edge at the end nearest the. needles.

from yet another aspect, therefore, the invention provides an attachment for a weft knitting machine adapted to forward an extra yarn to the knitting elements thereof, comprising positive feed means and a tube located between the feed means and the knitting elements the said tube being adapted to receive a stream of air to forward yarn from the positive feed means therethrough and having a cutting edge at the end nearest the knitting elements.

The positive feed means may comprise a paif of nip rolls one of which is driven. The driven roll may consist of two portions, an outer roll and an inner roll, the former being freely rotatable about the latter within limits determined by spring or pin means.

One method of carrying out the present invention will now be more fully described with reference to the accompanying drawings.

In the drawings:

FIG. 1 is a diagrammatic representation of a portion of a needle bed of a circular weft knitting machine and an attachment according to the present invention.

FIG. 2 illustrates one form of a driven nip roll which allows a varying rate of yarn feed.

FIG. 3 illustrates a further form of a driven nip roll.

FIG. 4 is a representation of a portion of knitted fa-bric according to the present invention.

In FIG. 1 a needle bed 1 of a circular weft knitting machine has cylinder and dial latch needles 2 and 3 respectively which knit the base fabric from the yarn 4. An extra yarn 5 is positively fed to an air ejector 6 by the nip rolls 7 and 8, the latter being a driven roll. The air ejector has a throat 9, compressed air inlet 10 and an outlet end 11 which is sharpened to give a cutting edge 12.

In operation the needles 2 and 3 knit a base fabric from the yarn 4 in the normal manner. The extra yarn 5 is positively fed by the nip rolls 7 and 8 to the air ejec tor 6 at a speed slower than the needles 2 and 3 take the yarn 4 from the supply. The yarn 5 passes through the throat 9 of the ejector and is forwarded by the air supply through the outlet end thereof and introduced to the needles 2 and 3 which then knit in this yarn with the yarn 4. Since the positive feed allows less yarn to pull through the nip than the needles require, yarn 5 is tensioned between the needles and the nip roll and is brought into contact with the cutting edge 12 of the outlet end of the ejector. When this tension is sufficiently great the yarn 5 is cut and the needles continue knitting yarn 4 only. As the positive feed forwards more yarn a fresh end is introduced to the needles and the sequence of events is repeated.

In order to obtain a random slubbing effect in the fabric the positive feed should be adapted to forward the yarn 5 to the knitting elements at an irregular rate. This can be achieved in a number of ways. The speed of the drive roll can be varied in a predetermined manner, or by varying the pressure between the nip rolls to allow the yarn 5 to occasionally slip through under the tension applied by the needles or the nip may be positively opened by cams operating on either or both rolls.

In a preferred embodiment either or both of the rolls, but most preferably only the driven roll, may have small flat portions machined thereon so that the yarn may be released at intervals. Preferably, again, the flat portions should not be more than /s apart, to prevent the appearance of uncontrolled one or two stitch slubs appearing in the fabric. In this embodiment the length of a slub is determined by the length of the fiat portions on the roll and the peripheral speed thereof. The frequency of slubs in a fabric course is determined by the number of fiat portions in the roll and the relative speeds of the knitting machine and the nip rolls.

It is clear that the more irregular the rate of feed of the yarn the more random the slubbing effect.

The above methods of varying the rate of feed of the extra yarn may also affect the length of the slub which is also dependent upon the distance between the knitting elements and the cutting edge of the air ejector, the distance between the positive feed and the knitting elements, and elasticity of the yarn.

The density of the slubs in the fabric depends on the speed of the yarn forming the base fabric compared with the average speed of the extra yarn, the relative denier of these yarns and the number of attachements per knitting position in action.

In FIGURE 2 the driven nip roll 8 of FIG. 1 is replaced by a composite roll comprising inner and outer portions 20 and 21, inner portion 20 being driven and outer portion 21 freely rotatable about the inner portion 20 within limits defined by the extension of the spring 22 which is attached to both portions 20 and 21.

As a result of the tension build up in the yarn caused by its being fed to the knitting elements at a slower rate than they require and the release of tension consequent upon the yarn being cut, the outer portion 21 tends to oscillate around the inner portion 20 thus having a varying circumferential speed. This results in a randomly varying rate of yarn fed to the knitting elements. The varying rate of feed causes the distance between the slubs and the slub length to vary also. Since the mean speed of the outer portion of the roll 21 is that of the driven inner portion 20, the amount of slub yarn fed into any yardage of knitted fabric is constant.

FIG. 4 is an alternative form of driven roll. In this form the outer portion 21 also surrounds the outer end of the driven portion 20 and contains slots 23, 24 and 25 cut through the face thereof to reveal inner portion 20, stud 26 passes through one of these slots, for example 23, and is located in the driven portion 20.

The operation of this roll'is similar to that of the driven roll of FIG. 3 except that the extent of oscillation is controlled by the length of the slot through which the stud 26 passes.

The following examples further illustrate the various aspects of the present invention.

EXAMPLE 1 In this example the attachment employed is that described with reference to FIG. 1 of the drawings. The nip rolls are 1 7 diameter and the driven roll 8 has flats /2" long cut in the periphery thereof.

With the knitting machine set to produce a double pique fabric and having one attachment, a basic yarn of 150 denier 30 filaments Crimplene is fed to the knitting elements at a speed of 350 ft. per minute with the machine running at 13 r.p.m. The extra yarn, a singles 36 worsted count low twist Terylene staple fibre is forwarded to the air ejector and then to the knitting elements via the nip rolls, the driven nip roll rotating at 100 r.p.m. This yarn is maintained with a high tension between the nip rolls and the yarn containing bobbin. As a result of the high tension in the yarn path the amount released by the fiats in the driven nip roll is irregular and hence a fabric is produced having a random slub effect.

4 FIG. 4 is a representation of a typical portion of knitted fabric, 30, produced by the process just described, the bars 31 representing the slubs.

EXAMPLE 2 The knitting machine is set up and operated as described in Example 1 and a 270 denier 20 filament polyhexamethylene adipamide yarn is knitted to form the base fabric and the slubs formed from a singles 36 Worsted count polyhexamethylene staple fibre yarn.

Although the fabric of this invention is preferably formed from a continuous filament bulked yarn, to form the base fabric, and a staple yarn as the extra yarn, staple yarn may also be employed in place of the continuous filament yarn and a continuous filament yarn in place of the staple yarn although this will be relatively much more difficult to break and may introduce considerable difficulty in knitting.

Varying fabric effects may be obtained by using yarns having different dye uptake or different filament crosssections as the base yarn and extra slub-forming yarn. Different fabric effects may also be obtained by using yarns having markedly different properties thus, for example, the base fabric may be formed from a bulked continuous filament polyhexamethylene adipamide yarn and the slub effect by a rayon staple fibre yarn.

What we claim is:

1. An attachment for a weft knitting machine having a plurality of knitting elements, said attachment adapted to forward an extra yarn to the said knitting elements and comprising: a positive yarn feed means which includes a pair of nip rolls one of which is driven; and a tube located between the feed means and the knitting elements; means for delivering a stream of air to said tube for forwarding the yarn from said feed means through said tube; and means defining a yarn cutting edge at the end of said tube nearest the knitting elements.

2. An attachment according to claim 1 wherein means is provided to vary the speed of the driven roll.

3. An attachment according to claim .1 wherein the nip may be positively open by cams operating on either or both rolls.

4. An attachment according to claim 1 wherein flat portions are machined on the peripheral surface or both of the nip rolls to allow yarn to be released at intervals.

5. An attachment according to claim 4 wherein the fiat portions are not more than A3" apart.

6. An attachment according to claim 1 wherein the driven roll comprises an outer and inner concentric roll, the former being freely rotatable about the latter, which is driven, within limits determined by a spring or pin means.

7. An attachment as in claim 1 including means associated with said nip rolls for forwarding the continuous extra yarn at a speed slower than the speed required by said knitting elements.

8. A process for manufacture of a weft knitted slub effect fabric comprising: knitting a yarn to form a base fabric which comprises a plurality of knitted courses; introducing an extra continuous yarn to the knitting elements during the knitting of one course of the fabric and knitting in with the first-mentioned yarn for a plurality of stitches; breaking and subsequently reintroducing the extra to the knitting elements to be knitted into the fabric again further along the course or in a subsequent course; and repeating at intervals the breaking and introduction of the extra yarn during the knitting of the fabric, the steps of introducing the extra yarn to the knitting elements and subsequently breaking and re-introducing the extra yarn being carried out by positively forwarding the extra yarn at a speed slower than the speed at which the knitting elements take the first-mentioned yarn, conducting the forward extra yarn with a fluid stream to the knitting elements whereby the extra yarn is tensioned, bringing the tensioned extra yarn into contact with a 6 cutting edge and subsequently reconducting the free end 2,130,770 9/1938 Lombardi 66-190 of the continuous extra yarn with the fluid stream to the 2,232,532 2/1941 Hunter 66-202 knitting elements. 2,260,117 10/ 1941 Marr 66-201 9. A process according to claim '8 wherein the yarn 3,099,907 8/1963 Ma ur l t 1, 66-125 XR forming the base fabric is a bulked contlnuous filament 5 FOREIGN PATENTS yarn and the extra yarn is a staple fibre yarn.

10. A process according to claim 8 wherein the extra ,069, 1 /1959 Germany. yarn is introduced to the knitting elements at an irregu- 926,857 5/ 1963 G e t Britain. lar rate. 597,024 8/ 1959 Italy.

References Cited UNITED STATES PATENTS 462,470 11/1891 Conde 66-201 US. Cl. X.R. 1,831,964 11/1931 Lombardi 66-19() 6 132 2,011,538 8/1935 Hausman 66-169 RONALD FELDBAUM, Primary Examiner 

